I've done some tinkering this month, though was out in Europe for two weeks for work and vacation during. I'll list out some observations and theories I have so far and planned next steps and would be great to hear feedback.
For the timing, the white marker is at the 0 degree mark. Got a pic of that here:
When I check the timing at idle, it looks pretty much at that white line, which would be no advance at all. If that's accurate, that would explain at least some of the poor idling.
Next, I checked vacuum, and this was kind of weird. My distributor has been hooked up to direct manifold vacuum via the 2nd port on my demon carb:
I disconnected that while idling and connected vacuum gauge to it. It read zero, needle didn't move at all, which was super strange. Giving throttle didn't change it at all. The gauge works, as when I flip it over to the first port (which is usually plugged), which is for ported vac, then it also reads zero but increases when I open the throttle.
So, I don't know how that second port which is supposed to be full manifold vac would have no vacuum at all. It must be clogged or blocked somehow? I think this would also explain the lack of advance at idle. If it was receiving true manifold vac at idle, there would be some additional advance at idle, but it's getting zero which retards the idle even more. I guess I need to pull the carb off to see if there's some blockage with that port, though the ported/timed one seems fine.
Since I couldn't use the manifold port on the carb to measure vac at idle, I connected to the port directly on the manifold (disconnecting the other stuff attached to that like the ram air actuators). It read between about 6 and 8 inches of mercury, which is pretty poor and I expect I want to be north of 12. Giving throttle would raise it a lot, then it would come back down to 6-8 range again at idle. I presume this is indicative of too little timing advance, as well, and increasing the advance would increase the vac and RPMs as it's struggling around 550-600 at idle now.
I replaced all the spark plugs with Autolite 25s and will replace the plug wires and cap/rotor next. There does seem to be a lot of brown/welded looking area on the terminal metal in the cap, so new one should help with spark quality I hope:
Here are what my plugs looked like if anyone can comment on what they show:
Another observation is that my battery ground cable only goes to the engine block. There's a small black wire that goes to chassis, but that seems pretty minimal vs other ones i've seen online where the big cable goes to chassis with a tab and then to engine block. Should I try to address this? I still have the issue with poor starting where it starts after I release the key from cranking.
Also, I smelled the engine oil and it definitely smelled like gas.
And, I checked voltage at the coil before/during/after startup. Before start with key in run, it gets 8-ish volts which seems right based on getting power via resistor. I had previously checked during crank (with starter motor disconnected) and it got full battery voltage, which made sense. Today, testing during cranking, it still got full voltage which seemed ok and there wasn't much voltage drop due to starter which was good. But, once engine was running and key in run while idling and voltage was still full battery, which I wasn't expecting. I was expecting it to be at the reduced voltage via the resistor, but didn't seem to be the case. I'm getting a new multimeter and will check this again next time.
So my current plans of next actions are:
- change oil/filter (I haven't done this yet since getting it)
- replace plug wires and cap/rotor.
- advance the timing to at least 6 degrees w/o vacuum advance and see what that gets me in terms of better idling, higher RPM, and higher vacuum.
- *question*: should also disconnect the PCV at the back of carb while setting idle timing and checking vacuum? I suppose there's possibility of vacuum leak there which that would eliminate?
- I have a new clear fuel filter coming and will add a fuel pressure gauge.
I still have the mystery of no vac from manifold port on the carb, so removing the carb i'll look into that. I have rebuild kit so will also do clean/rebuild if other things don't help enough.
For the timing, the white marker is at the 0 degree mark. Got a pic of that here:
When I check the timing at idle, it looks pretty much at that white line, which would be no advance at all. If that's accurate, that would explain at least some of the poor idling.
Next, I checked vacuum, and this was kind of weird. My distributor has been hooked up to direct manifold vacuum via the 2nd port on my demon carb:
I disconnected that while idling and connected vacuum gauge to it. It read zero, needle didn't move at all, which was super strange. Giving throttle didn't change it at all. The gauge works, as when I flip it over to the first port (which is usually plugged), which is for ported vac, then it also reads zero but increases when I open the throttle.
So, I don't know how that second port which is supposed to be full manifold vac would have no vacuum at all. It must be clogged or blocked somehow? I think this would also explain the lack of advance at idle. If it was receiving true manifold vac at idle, there would be some additional advance at idle, but it's getting zero which retards the idle even more. I guess I need to pull the carb off to see if there's some blockage with that port, though the ported/timed one seems fine.
Since I couldn't use the manifold port on the carb to measure vac at idle, I connected to the port directly on the manifold (disconnecting the other stuff attached to that like the ram air actuators). It read between about 6 and 8 inches of mercury, which is pretty poor and I expect I want to be north of 12. Giving throttle would raise it a lot, then it would come back down to 6-8 range again at idle. I presume this is indicative of too little timing advance, as well, and increasing the advance would increase the vac and RPMs as it's struggling around 550-600 at idle now.
I replaced all the spark plugs with Autolite 25s and will replace the plug wires and cap/rotor next. There does seem to be a lot of brown/welded looking area on the terminal metal in the cap, so new one should help with spark quality I hope:
Here are what my plugs looked like if anyone can comment on what they show:
Another observation is that my battery ground cable only goes to the engine block. There's a small black wire that goes to chassis, but that seems pretty minimal vs other ones i've seen online where the big cable goes to chassis with a tab and then to engine block. Should I try to address this? I still have the issue with poor starting where it starts after I release the key from cranking.
Also, I smelled the engine oil and it definitely smelled like gas.
And, I checked voltage at the coil before/during/after startup. Before start with key in run, it gets 8-ish volts which seems right based on getting power via resistor. I had previously checked during crank (with starter motor disconnected) and it got full battery voltage, which made sense. Today, testing during cranking, it still got full voltage which seemed ok and there wasn't much voltage drop due to starter which was good. But, once engine was running and key in run while idling and voltage was still full battery, which I wasn't expecting. I was expecting it to be at the reduced voltage via the resistor, but didn't seem to be the case. I'm getting a new multimeter and will check this again next time.
So my current plans of next actions are:
- change oil/filter (I haven't done this yet since getting it)
- replace plug wires and cap/rotor.
- advance the timing to at least 6 degrees w/o vacuum advance and see what that gets me in terms of better idling, higher RPM, and higher vacuum.
- *question*: should also disconnect the PCV at the back of carb while setting idle timing and checking vacuum? I suppose there's possibility of vacuum leak there which that would eliminate?
- I have a new clear fuel filter coming and will add a fuel pressure gauge.
I still have the mystery of no vac from manifold port on the carb, so removing the carb i'll look into that. I have rebuild kit so will also do clean/rebuild if other things don't help enough.
